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Discussion Starter · #1 ·
My latest design project will have one of these.
My client managed to get his hands on a used Square D I-Line panelboard lineup. From Square D delivery would be well over a year. He will get his in January of the coming year! The shop providing the equipment had been around over 50 years and knows what they are doing. The only negative is I would have ordered one with a cable entry section like I used on previous projects. This one is set up for cable entry behind the main breaker. The bus bars are barely 24” from the floor! Any way you look at it the electrician will need ape arms. My concern is that the likelihood of conductor and primarily insulation damage trying to bend and shape large cables to connect to the bus.

Reference the photo of similar gear.

Originally, I was going to use 10 – 600 MCM per phase with a 3/0 neural. But, coming out of 10 - 3-1/2” PVC conduits from below will be a nightmare. At best, with all the different phases crisscrossing each other, avoiding damage to the insulation will be unlikely. And maintaining equal phase conductor length? HA! The service transformer is a pad mount that is only 20 feet away.
One night when I couldn’t get to sleep, I think I came up with what I thing is a workable solution! How about using 12 - 500 MCM in 3-1/2” PVC conduits and coming up out of the floor directly under the phase bus bars, each conduit with only it’s respective phase conductors! Minimal bending of the conductors to lay onto the bus above. Little chance of damage and no crisscrossing. And maintaining equal phase lengths possible. Each conduit would have 4 – 500 MCM same phase conductors.
The system 3/0 neutrals would be in their own 3 – 3-1/2” PVC conduits and terminate to the neutral bus.
Of course, NO ferrous metal ever between the separated phase conductors!

Thoughts?
Wood Fixture Electrical wiring Composite material Engineering
 

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Power distribution and controls
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USED?????? Why such a long lead time? How old is this gear?

What documentation is the vendor supplying? Or are you going to pay someone to commission the gear including all of the testing? (meger, hi pot, dlro, coordination study for the breakers)
What breakers and trip units are supplied?

Put the section on a 12" pad if your worried.

You would be much better off if the transformer was farther away. Then you could criss cross the primary conduit under ground. Which makes the cable length much easier to deal with.

I did on primary feed where the shortest and longest conductors where 23' different. I was told to cut the long ones and refused.

I have done 100's of sections like that with the primary conduits in the same section as the MCB.
Just need a good measure of working clearances to pull and make up the conductors.

Who is going to stamp these drawings?


Are you NUTS about putting filling a conduit with ONLY ONE PHASE CONDUCTOR?
or did I mis understand your text?
That is a motor winding looking for a fault. I have seen what happens. It is very expensive to fix and the last guy I know that did it lost his Arizona engineering license.
 

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USED?????? Why such a long lead time? How old is this gear?

What documentation is the vendor supplying? Or are you going to pay someone to commission the gear including all of the testing? (meger, hi pot, dlro, coordination study for the breakers)
What breakers and trip units are supplied?

Put the section on a 12" pad if your worried.

You would be much better off if the transformer was farther away. Then you could criss cross the primary conduit under ground. Which makes the cable length much easier to deal with.

I did on primary feed where the shortest and longest conductors where 23' different. I was told to cut the long ones and refused.

I have done 100's of sections like that with the primary conduits in the same section as the MCB.
Just need a good measure of working clearances to pull and make up the conductors.

Who is going to stamp these drawings?


Are you NUTS about putting filling a conduit with ONLY ONE PHASE CONDUCTOR?
or did I mis understand your text?
That is a motor winding looking for a fault. I have seen what happens. It is very expensive to fix and the last guy I know that did it lost his Arizona engineering license.
Have you tried to order new gear recently? When vendors stop quoting projects because they can't project lead times, the market is definitely screwed up. Sometimes you do what has to be done to make things work. Invariably these days there is one stupid little part that will keep you from having a complete gear assembly, like perhaps the cover will be available 6 months to a year from now.

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Power distribution and controls
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I have purchased over 30 large amp or MV switchgear assemblies. No where did I say it was a bad idea, I was trying to bring out the amount of checks/tests that will have to be done before energizing. I come from the, " if you can not measure it you can not manage it" school of thought.
Some of the older switch gear products are far better that what is built today.
I had/have a customer in Mexico that would/does call me for old Westinghouse products. Got most of the sections from my local PEARL dealer. (PEARL – Professional Electrical Apparatus Reconditioning League) Never had much trouble with the mechanics, the trip modules were a different issue entirely. Worst thing was getting the paint to match. I know a guy that can do powder coating like the factories do. Even though the sheet metal looked new I made it clear the sections were used and reconditioned.
 

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Discussion Starter · #5 ·
USED?????? Why such a long lead time? How old is this gear?

What documentation is the vendor supplying? Or are you going to pay someone to commission the gear including all of the testing? (meger, hi pot, dlro, coordination study for the breakers)
What breakers and trip units are supplied?

Put the section on a 12" pad if your worried.

You would be much better off if the transformer was farther away. Then you could criss cross the primary conduit under ground. Which makes the cable length much easier to deal with.

I did on primary feed where the shortest and longest conductors where 23' different. I was told to cut the long ones and refused.

I have done 100's of sections like that with the primary conduits in the same section as the MCB.
Just need a good measure of working clearances to pull and make up the conductors.

Who is going to stamp these drawings?


Are you NUTS about putting filling a conduit with ONLY ONE PHASE CONDUCTOR?
or did I mis understand your text?
That is a motor winding looking for a fault. I have seen what happens. It is very expensive to fix and the last guy I know that did it lost his Arizona engineering license.
I have no problem with that. Look up "Iso phase bus duct". The CONCEPT has been around a very long time.
So long as you keep no ferrous metals between the phases, you are fine.

For example, im this case the "A" phase conduits would be right below the "A" phase bus bar. Straight up, connect. No crisscrossing, no sharp bends, etc.
 

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motors and controls.........
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300.3(B)(1) Exception specifically allows conductors of each phase to be in PVC. I've done it a few times and I've seen the PUCO do it as well. As long as there is absolutely no ferrous metal nearby, it'll be ok.
 

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Discussion Starter · #8 ·
Thanks for all your responses!
It's still going to be hard to keep the phase conductors the same length. And to make sure the utility people don't try to cut the ends to the same length!

RC
 

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USED?????? Why such a long lead time? How old is this gear?
What documentation is the vendor supplying? Or are you going to pay someone to commission the gear including all of the testing? (meger, hi pot, dlro, coordination study for the breakers)
What breakers and trip units are supplied?


I would recommend HIGHLY verifying AIC before purchase.
Everything has long lead times.
I would fully test this gear and while I would prefer documentation in my experience many firms selling used equipment do not fully test, so I would do any and all testing.
NO HI-POT at 480/277



Who is going to stamp these drawings?
I would or I would pay an engineer, depending on the jurisdiction.
 

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Discussion Starter · #10 ·
BTW, I am the PE of record on this project. And I will have no issues in stamping the drawings.

The company we are getting the gear from has been in business for over 50 years and we have done business with them before and were very pleased with he product. They have been doing regular testing on my clients electrical equipment for many years. I have used them to test equipment on other projects of mine. Good people. They are members of PEARL and NETA.

I will be doing the coordination study.

The main will have a remote trip located in a KNOX box outside the building, a maintenance mode switch, and ground fault. The existing trip unit will be replaced.

RC
 
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